The present application relates to a display device which incorporates an image pickup function for optically detecting an external proximity object, a method of driving the same, and an electronic device including the same.
In recent years, a display device in which information input is enabled has attracted attention. In this display device, a touch detecting function detecting a contact of a finger or the like is equipped in a display device such as a liquid crystal display device, and various button images are displayed on that display device, instead of using typical mechanical buttons. In the display device having such a touch detecting function, since an input device such as a keyboard, a mouse, and a keypad is not necessary, there is a tendency that use of the display device is expanded in a portable information terminal such as a portable phone in addition to a computer.
There are several methods in touch detecting methods, and one of them is an optical method. In the display device having such an optical touch detecting function, for example, there is a display device in which light emitted from the display device, and reflected by the external proximity object in the vicinity of a display surface is detected by a photo-detector incorporated in the display device, and the external proximity object is detected based on a light amount. For example, in Japanese Unexamined Patent Publication No. 2008-205870, the display device which incorporates the image pickup function is proposed. In that image pickup function, a photoelectric conversion element is used as the photo-detector, and electric charges supplied from the photoelectric conversion element are stored for charging in a capacitor during a predetermined period, thereby detecting the external proximity object based on the amount of electric charges.